From mboxrd@z Thu Jan 1 00:00:00 1970 From: Chris Bainbridge Subject: [PATCH] ACPI/sbshc: Add 5us delay to fix SBS hang on MacBook Date: Wed, 29 Apr 2015 21:21:40 +0100 Message-ID: <20150429202140.GB25904@localhost> References: <20150424012530.GA16763@localhost> <4435249.leKkNHm9IZ@vostro.rjw.lan> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from mail-wi0-f174.google.com ([209.85.212.174]:36497 "EHLO mail-wi0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750737AbbD2UVp (ORCPT ); Wed, 29 Apr 2015 16:21:45 -0400 Received: by wizk4 with SMTP id k4so194355188wiz.1 for ; Wed, 29 Apr 2015 13:21:44 -0700 (PDT) Content-Disposition: inline In-Reply-To: <4435249.leKkNHm9IZ@vostro.rjw.lan> Sender: linux-acpi-owner@vger.kernel.org List-Id: linux-acpi@vger.kernel.org To: "Rafael J. Wysocki" Cc: Len Brown , linux-acpi@vger.kernel.org Regression in commit 7bc5a2bad0b8d9d1ac9f7b8b33150e4ddf197334 Author: Matthew Garrett Date: Sat Sep 20 13:19:47 2014 +0200 ACPI: Support _OSI("Darwin") correctly Supporting _OSI("Darwin") caused the MacBook firmware to expose the SBS, resulting in intermittent hangs of several minutes on boot, and failure to detect or report the battery. Fix this by adding a 5us delay to the start of each SMBUS transaction. This timing is the result of experimentation - hangs were observed with 3us but never with 5us. Link: https://bugzilla.kernel.org/show_bug.cgi?id=94651 Signed-off-by: Chris Bainbridge --- drivers/acpi/sbshc.c | 22 ++++++++++++++++++++++ 1 file changed, 22 insertions(+) diff --git a/drivers/acpi/sbshc.c b/drivers/acpi/sbshc.c index 26e5b50..bf034f8 100644 --- a/drivers/acpi/sbshc.c +++ b/drivers/acpi/sbshc.c @@ -14,6 +14,7 @@ #include #include #include +#include #include "sbshc.h" #define PREFIX "ACPI: " @@ -87,6 +88,8 @@ enum acpi_smb_offset { ACPI_SMB_ALARM_DATA = 0x26, /* 2 bytes alarm data */ }; +static bool macbook; + static inline int smb_hc_read(struct acpi_smb_hc *hc, u8 address, u8 *data) { return ec_read(hc->offset + address, data); @@ -132,6 +135,8 @@ static int acpi_smbus_transaction(struct acpi_smb_hc *hc, u8 protocol, } mutex_lock(&hc->lock); + if (macbook) + udelay(5); if (smb_hc_read(hc, ACPI_SMB_PROTOCOL, &temp)) goto end; if (temp) { @@ -257,12 +262,29 @@ extern int acpi_ec_add_query_handler(struct acpi_ec *ec, u8 query_bit, acpi_handle handle, acpi_ec_query_func func, void *data); +static int macbook_dmi_match(const struct dmi_system_id *d) +{ + pr_debug("Detected MacBook, enabling workaround\n"); + macbook = true; + return 0; +} + +static struct dmi_system_id acpi_smbus_dmi_table[] = { + { macbook_dmi_match, "Apple MacBook", { + DMI_MATCH(DMI_BOARD_VENDOR, "Apple"), + DMI_MATCH(DMI_PRODUCT_NAME, "MacBook") }, + }, + { }, +}; + static int acpi_smbus_hc_add(struct acpi_device *device) { int status; unsigned long long val; struct acpi_smb_hc *hc; + dmi_check_system(acpi_smbus_dmi_table); + if (!device) return -EINVAL; -- 2.1.4